SimpleChIP^® Human Bivalent Promoter Assay Kit #8982

The nucleosome, made up of four core histone proteins (H2A, H2B, H3 and H4), is the primary building block of chromatin. Originally thought to function as a static scaffold for DNA packaging, histones have now been shown to be dynamic proteins, undergoing multiple types of post-translational modifications, including acetylation, phosphorylation, methylation and ubiquitination (1). Histone methylation is a major determinant for the formation of active and inactive regions of the genome and is crucial for the proper programming of the genome during development (2,3). Trithorax proteins catalyze the tri-methylation of histone H3 Lys4, a mark of transcriptional activation, while polycomb proteins establish and maintain tri-methylation of histone H3 Lys27, a mark of transcriptional repression (4,5). Though originally thought to be mutually exclusive, recent studies have shown that in stem cells certain developmental genes and highly conserved non-coding elements contain both of these marks (6-8). These ‘bivalent’ regions of the genome are poised for activation and are thought to hold the key to the vast potential of stem cells. As stem cells differentiate along a given lineage, many bivalent genes become monovalent, either retaining the tri-methyl histone H3 Lys4 mark if activated during differentiation, or the tri-methyl-histone H3 Lys27 mark if repressed. Chromatin immunoprecipitation (ChIP) is a powerful technique that can be used to identify bivalent domains in stem cells and changes in bivalency that occur during differentiation (6-8).